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Evaluating iron deficiency
Monitoring treatment and environmental intervention of chronic lead poisoning
The porphyrins are intermediaries in the heme synthesis pathway. When iron is not available for heme synthesis (eg, iron deficiency), zinc protoporphyrin (ZPP) accumulates within RBCs. Lead inhibits several enzymes in the heme synthesis pathway and causes increased levels of RBC ZPP.
ZPP is a biological marker of lead toxicity and was previously used, in conjunction with blood lead assays, to screen for lead poisoning in children. However, because of poor sensitivity and specificity, ZPP is no longer recommended for lead screening in children. However, ZPP remains a useful tool for monitoring treatment of individuals with confirmed elevated lead levels.
<70 mcmol ZPP/mol heme
An elevated zinc protoporphyrin (ZPP) indicates impairment of the heme biosynthetic pathway.
Elevated ZPP levels in adults may indicate long-term (chronic) lead exposure or may be indicative of iron deficiency anemia or anemia of chronic disease.
High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, it is suggested a specimen not be collected for 96 hours.
1. Stanton NV, Gunter EW, Parsons PJ, et al: Empirically determined lead-poisoning screening cutoff for the Protofluor-Z hematofluorometer. Clin Chem 1989;35(10):2104–2107
2. Rosen JF: Preventing Lead Poisoning in Young Children. US Public Health Service, Centers for Disease Control, Atlanta, GA, 1991
3. Occupational Safety and Health Administration: OSHA Lead Standard-Requirements from the General Industry Standards Lead (1910, 1025), from 29 CFR 1910, 1025, A.M. Best Safety and Security-2000. Available from URL: ambest.com/safety/osha/chap10g.html Retrieved March 2000
4. Centers for Disease Control and Prevention. Screening Young Children for Lead Poisoning. Guidance for State and Local Public Health Officials. Atlanta, GA: US Dept of Health and Human Services. Public Health Service: November 1997 Available from URL: cdc.gov/nceh/lead/guide/guide97.htm